The US has issued a sharp rebuke to Bahrain after a day of crackdowns on demonstrators, in which hospitals were blockaded by riot police, scores of people were wounded and the Shia diaspora condemned the kingdom's rulers.

The capital, Manama, was under curfew from 4pm to 4am, and the government was using emergency laws to ban public gatherings. The central square known as Pearl Roundabout, which had been a base for the protest movement, was violently cleared by riot police.

Troops and riot police then moved on to locations across the city, including the Salmaniya medical clinic , which had become a second focal point of demonstrations. Doctors reported being attacked in wards and claimed power to part of the hospital had been turned off. The government said it was pursuing "thugs and outlaws".

"We have been chased, attacked and locked inside the grounds," one doctor told the Guardian. "But the worst thing is … that we have been stopped from reaching patients."

On Wednesday night the British government said it would charter planes to evacuate its citizens who want to flee the deteriorating situation in Bahrain. The Foreign Office has urged people to leave the country on commercial flights but those who cannot get a ticket will be evacuated on a Foreign Office-chartered flight costing £260.

Phone lines to Bahrain appeared blocked for much of the day , making it difficult to confirm reports of attacks on demonstrators. However, videos uploaded to YouTube and Facebook showed clear violence against unarmed protesters – including one man shot in the leg from at least 100 metres away. In another case, men in riot police uniform vandalised parked cars as they confronted demonstrators.

The US secretary of state, Hillary Clinton, led diplomatic reaction to the violence, delivering a stern warning to Bahrain's rulers. Clinton said Bahrain, and neighbouring Gulf states that have sent troops to help quell the uprising, were "on the wrong track". She demanded that Bahrain show restraint with demonstrators and keep hospitals open.

She described the situation in Manama as alarming and condemned the use of force against demonstrators. She said four Gulf states had sent troops to Bahrain. Only Saudi Arabia has so far publicly acknowledged doing so.

In the UK, William Hague, the foreign secretary, said Britain would review arms sales to Bahrain and Libya, including crowd control equipment which has been used against unarmed protesters.

Iran, meanwhile, ratcheted up its rhetoric, labelling the damage done to diplomatic relations as "irreparable". In Iraq and Lebanon, the Shia leaders Muqtada al-Sadr and Hassan Nasrallah criticised the attacks in comments that underscored sectarian undertones. "They attack us because we are Shia and our presence threatens them," said Hussein Mehdi, a protester shot in the leg by birdshot on Tuesday. "The Saudis are the ones who have driven this. They are taking a hard line and the regime answers to them."

Saudi Arabia's stance has been the subject of much speculation among demonstrators, who felt they had established trust with Bahrain's crown prince, Sheikh Salman bin Hamad bin Isa al-Khalifa .

Saudi Arabia has a restive Shia minority near its border with Bahrain, which accounts for roughly 12% of its population. Saudi's rulers have long viewed the Shia as a potential threat. Commentators say Riyadh was not prepared to tolerate demonstrations that would weaken it by proxy and empower its arch foe, Iran.